Dual rotor machine gun



July 26, 1966 w. E. MARTWICK ET 3,252,367

DUAL ROTOR MACHINE GUN Original Filed March 18, 1964 INVENTOR. WILFORDE. MARTWICK a DUANE C. YOUMANS BY mwyzg mul ATTORNEY United StatesPatent 3,262,367 DUAL ROTOR MACHINE GUN Wilford E. Martwick,Minneapolis, and Duane C. You- This application is a continuation of ourcopending application Serial No. 352,999, filed March 18, 1964, nowabandoned, for Rapid Fire Weapon. The invention concerns an improvedmechanism for operating a machine gun in which cartridges are fedbetween a pair 'of rotating cylinders, each having a plurality ofequally spaced half cartridge chambers formed in the periphery thereof,that are rotated into positions adjacent each other to form a completesingle chamber from which a cartridge is fired.

Modern machine guns generally utilize a reciprocating mechanism to feedand fire cartridges that are supplied from a drum orfrom a belt. Asliding bolt pushes the cartridges into a breech chamber that surroundsand supports the cartridge. The bolt itself serves as a support for therear of the cartridge during firing. Since the cartridge is fullysurrounded and supported by the breech and bolt assembly, the fullexplosive power of the propellant is applied to the bullet. Theexpanding gas cannot escape from the sealed chamber, and the cartridgeitself cannot rupture because of the supporting structure surroundingthe cartridge. Although these reciprocating mechanisms are somewhatcomplicated, they are in wide use today because of the reliability andspeed which have been engineered into them.

The prior art reveals that the reciprocating mechanism is but one of themany different mechanisms that have been invented for the purpose offiring cartridges in rapid succession. Many of these other mechanismswere inherently less complicated than the reciprocating mechanism, butmost of them never came into popular usage. In many cases, one or twoflaws in an otherwise excellent idea prevented acceptance of the idea.

The present invention provides a mechanism to correct an important fiawin an early approach to achieving rapid fire. The basic system includesa pair of rotatable rotors or cylinders that are mounted on parallelshafts in a suitable frame. Both cylinders are of generally circularcross-section, and each has a plurality of equally spaced half cartridgechambers formed in the periphery thereof parallel to the shafts aboutwhich the cylinders rotate. One cylinder is mounted directly above theother cylinder with its lower surface adjoining the upper surface of thelower cylinder. Means are provided to rotate the two cylinders inopposite directions, such that half chambers from the upper cylinder arepositioned adjacent corresponding half chambers on the lower cylinder toform a complete cartridge chamber. Cartridges are fed between thecylinders from the side, and means are provided to fire each cartridgeafter the complete cylinder has surrounded the cartridge.

This basic system is set forth in the Glov Patent 1,164,- 498, whichissued December 14, 1915. In theGlov patent, both the upper and thelower cylinder are directly geared to a Geneva mechanism that is drivenby a hand crank. The Geneva mechanism converts the continuous rotationof the hand crank into intermittent rotation of the two cylinders. Adwell period is provided each time two half chambers coincide to form afull chamber. During this dwell period a firing pin is activated to firethe cartridge. The rotation then continues to place a second pair ofhalf chambers in conjunction at which time another dwell period isprovided for firing the second cartridge.

In the Glov device the lower cylinder picks up a cartridge from a drumthat is mounted on the side of the weapon. The cartridge is carried bythe lower cylinder into position to be fired.

The Glov magazine gun is basically a desirable weapon because of itssimplicity. There are relatively few moving parts, the parts themselvesare not complicated to manufacture or assemble, and the mechanism doesnot operate at the extremely rapid rate that is necessary in thereciprocating type of machine gun. Wear and tear on the individualcomponents is thus reduced considerably.

As previously mentioned, the present invention utilizes the same basicstructure as that disclosed by Glov. There is a basic flaw, however, inthe Glov device which renders it almost useless as a practical weapon.

The flaw in the Glov device results from the fact that the two cylindersrotate about parallel shafts that are mounted in the frame at a fixeddistance apart. The two cylinders are thus at a fixed distance apartduring firing and during rotation. In such a system it is impossible toseal the cartridge chamber during firing.

If the geometry of the system is analyzed, -the fact that the cartridgechamber cannot be sealed becomes clearly apparent. The two circularcylinders are mounted on parallel shafts that are at a distance apartequal to the sum of the radii of the two cylinders. With thisconfiguration, the outer surfaces of the two cylinders make contactalong a line that is formed by a plane containing the two shafts. Thetwo shafts must be at least this distance apart in order to preventinterference of the surfaces of the cylinders during rotation. When thetwo concave half cartridge chambers, which are formed in opposingcylinders, are positioned adjacent each other to form a completechamber, each of the half chambers is bisected by the previouslymentioned plane. Since the two surfaces can meet only where theyintersect the plane, it is obvious that the junction between the edgesof opposing half chambers will be slightly open. This physical structurecan be clearly seen in FIGURE 2 of the Glov patent.

These openings in the junctions between the opposing edges of theadjacent half chambers result in an inoperable weapon for all practicalpurposes. Each time the cartridge is fired a large amount of gas willescape from these openings. Because of the high pressures formed in thechamber, the large amount of gas escaping during rapid fire of theweapon would generate an intolerable environment for the operator of theweapon. In addition, the loss of pressure would degrade the performanceof the bullet. An even more serious problem is the fact that mostcartridge cases are not designed to withstand the pressures developedduring firing. The cartridges are designed to be completely surroundedby the walls of the breech chamber during firing. It is probable thatmany of the cartridges being fired from the Glov magazine gun wouldrupture during firing. The ruptured cartridges would be dangerous to theoperator, and could also foul the mechanism of the gun.

The present invention removes this flaw in the system by providing amechanism for tightly sealing the chamber during firing. This scalingfunction is provided by mounting the upper rotor on a shaft that isallowed limited movement in the plane containing the axes of the twoshafts, and in a direction perpendicular to the two axes. The range ofmotion is such that the upper cylinder can be pressed firmly against thelower cylinder during the dwell period to seal tightly the junctionbetween the adjoining edges of the adjacent half chambers. Duringrotation of the cylinders, the upper cylinder isjfree to move upwardlyso that the adjoining surfaces of the cylinders will not bind. The exactmechanism for accomplishing this alternate locking and releasing of theupper 3 cylinder will be explained in detail in a later portion of thespecification.

In the present invention, the upper cylinder is not geared directly tothe drive mechanism that operates the lower cylinder as it is in theGlov devices. The cartridges are also inserted between the two cylindersby means of a cartridge belt rather than from a magazine. In the lowercylinder, which in this invention is driven through a Geneva mechanismby a hand crank, the half chambers mesh with the cartridges in the beltto draw the cartridges into the firing position. The cartridges in turnmesh with the half chambers in the upper cylinder to effect itsrotation.

It is therefore a primary object of the present invention to improve theoperation of a rapid fire weapon utilizing a pair of revolving cylindersin which concave half cartridge, chambersformed in the surface, of eachcylinder. are.

joined to form a complete cartn'dge chamber, by providing a mechanismwhich will seal the junction between the half chambers during firing,and allow separation of the cylinders during rotation to preventinterference between the surfaces thereof.

A further object of the present invention is to provide a new and moreeffective means of sealing the junction between the half cartridgechambers during firing of a split breech weapon.

These and other objects of the present invention will become apparentwhen considered in view of'the accompanying drawings in which:

FIGURE 1 is a side view of the rapid fire weapon from which the outsideshell or cover has been removed to show the firing mechanism in detail;

FIGURE 2 is a cut away front view of the weapon taken generally alongline 22 of FIGURE 1; and

FIGURE 3 is a sectional side view of the two revolving cylinders orrotors and the sliding cam member used to lock the rotors during firing,taken along line 33 of FIGURE 2.

Referring now to the drawing, there is disclosed in FIGURE 1 a side viewof the subject invention. An upper rotor or cylinder 10 and a lowerrotor or cylinder 11 are mounted in a frame which includes a forwardmember 12, a rear member 113, an upper member 14, and a lower member 16.The frame members are firmly connected together by screws, such as 17(FIGURE 2), to form a chamber 313 in which rotors 10 and 11 are mounted.Attached to the front of forward frame member 12 is a barrel 19 having abore therein (not shown). Barrel 1-9 is firmly attached to front member12 by an annular housing member 21.

Referring now to FIGURE 2, it can be seen that rotor 10 is mounted forrotation in chamber 18 on a shaft 22. Rotor 11 is mounted for rotationin chamber .18 on a shaft 23 that is journalled in rear frame member 13and forward frame member 12. Shafts 22 and 23 are mounted in parallel inthe frame, with shaft 22 being directly above shaft 23.

FIGURES l and 2 disclose that rotors 10 and 11 have a generallycylindrical configuration, and have a nominal circular cross-section.Formed about the periphery or surface of rotors 110 and 11 in parallelwith shafts 22 and 23 are a plurality of concave half cartridge chamberssuch as 24 and 26. In the preferred embodiment disclosed herein, thereare six such half chambers evenly spaced around the periphery of eachrotor.

FIGURE 1 discloses a mechanism for rotating rotors 10 and 11. Thedriving mechanism is mounted on a support member 27, which is bolted tothe rear of frame member 13. A hand crank 28 provides the motive powerfor the weapon as it is revolved in a clockwise direction as seen inFIGURE 1. This rotation of hand crank 28 is transferred to a drive shaft29 through a bevel gear 31 and a similar bevel gear on drive shaft 29(not shown). Attached to the end of drive shaft 29 adjacent frame member13- is a drive cam 32 which engages a Geneva star wheel 33 mounted onshaft 23. The con- 4 tinuous rotation of drive shaft 29 is thusconverted into intermittent rotation of shaft 23'and rotor 11 by Genevawheel 33 in a manner well known in the art.

As rotor 11 is revolved in a clockwise direction, as shown in FIGURE 2,by Geneva wheel 33-, the half chambers therein mesh with cartridgescarried by a cartridge belt 34. Thus, in FIGURE 2, a cartridge 36 hasbeen carried between the rotors by a half chamber 37 and a new cartridge38 will be carried between the rotors by a half chamber 39 as therotation of rotor 11 continues.

Upper rotor 10 is not driven directly by hand crank 28 and theassociated driving means. Rotor 10 is driven in a counterclockwisedirection as viewed in FIGURE 2 by the meshing of the half chambers inrotor 10 with thecartridges beingpulledbetween the rotors by rotor 11.For example, as cartridge 36 is expelled from between the rotors by therotation of rotor 11, .a counterclockwise rotation is imparted to rotor10. As cartridge 38 is drawn between the rotors, it will mesh with \ahalf chamber 41 in rotor 10 to continue this counterclockwise rotation.

The drive mechanism is constructed such the intermittent revolution ofthe rotors is achieved. As the rotors reach the position shown in FIGURE2, the Geneva drive is scheduled to reach its dwell period. During thisdwell period, the firing of the cartridge takes place. In FIGURE 1, aspring loaded firing pin 42 is mounted on support member 27 and rearframe member 13. A cam follower 43 mounted on firing pin 42 rides thesurface of a ramp on drive cam 32. As drive shaft 29 is rotated, camfollower 43 gradually forces firing pin 42 to the rear against theaction of the spring. When the dwell period is reached, cam follower 43reaches the high point of the ramp on drive cam 32 and is suddenlyreleased to allow the firing pin to activate the ignitor of thecartridge. so that each time a new cartridge reaches the position ofcartridge 36 in FIGURE 2, the firing pin is released.

After each cartridge is fired, Geneva wheel 33 again imparts rotation torotor 11. It is obvious from FIG- URE 2 that such further rotation wouldnot be possible unless means were provided to increase the distancebetween shafts 22 and 23. The sum of a radius 46 of rotor 10 and aradius 47 of rotor 11 is obviously greater than the distance betweenshafts 22 and 23. The outer surfaces of rotors 10 and 11 would thus bindunless the two rotors were separated during rotation. I

In order to allow separation of rotors 10 and 11 during rotation, rotor10 is mounted on shaft 22, which in turn is mounted in the frame forlimited movement in a plane containing the axes of the two shafts and ina direction perpendicular to the axes. This translational movement ofrotor 10 is sufiicient to allow rotor 10 to move from the position shownin FIGURE 2 to a position in which shafts 22 and 23 are at a distanceapart greater than the sum of radius 46 and radius 47.

The mechanism which controls the translational movement of rotor 10 isdisclosed in FIGURES l and 3. FIGURE 3 discloses that shaft 22 issupported in the frame by a shifting cam member 51 that is insertedlongitudinally through a slot in shaft 22. Cam member 51 islongitudinally movable within the slot in shaft 22. In the positionshown in FIGURE 3, cam member 51 has .a high portion 51a thereon incontact with a stop 52 that is mounted on rear member 13. Anintermediate portion 51b on the opposite end of cam member 51 alsoengages the upper surface of a slot in forward member 12. In thisposition, cam member 51 firmly locks rotor 10 in the position shown inFIGURE 2. This locked position, which occurs during the dwell period,effectively seals the chamber which surrounds cartridge 36 duringfiring. In FIGURE 2 this chamber is formed by half chamber 37 and halfchamber 40. The junction between half chamber 37 and half chamber 40 isformed by a The mechanism is synchronized URE 3.

pair of flat surfaces 37a and 40a that have been formed along a lineperpendicular to the plane that contains the axis of shaft 22 and shaft23. In this manner arelatively wide junction surface on each side ofcartridge 36 is obtained in order to effectively seal the cartridgechamber and support cartridge 36. Cam member 51 is thus constructed suchthat it will apply a predetermined amount of pressure downward on rotorin order to effectively seal the chamber.

After the dwell period, during which firing of the cartridge occurs,Geneva wheel 33 again begins to rotate rotor 11. Before this rotationcan begin, however, rotor 10 must be free to move upwardly. This isaccomplished by moving cam member 51 to the left, as shown in FIG- Ascam member 51 moves to the left, high portion 51a and intermediateportion 51b are removed from their position in contact with the frame.Intermediate portion 51b now comes in line with stop 52, and a lowerportion 510 is positioned in the slot in frame 12. Rotor 10 is now freeto move upwardly the required distance, as the outer surfaces of the tworotors begin to bind during rotation.

This movement of cam member 51 must of course be synchronized with therotation of the rotors. The mechanism for accomplishing thissynchronization is disclosed in FIGURE 1. The mechanism includes arocker arm 53 that is pivotally mounted on a support member 54attached-to rear member 13. Attached to the rear of sliding cam member51 is a cross member 56 having a slot 57 therein. A cam follower end 58of rocker arm 53 is positioned within slot 57. Mounted on shaft 29 is aguide cam 59 having a rear member 61' and a forward member 62.Positioned between members 61 and 62 is a cam follower end 63 of rockerarm 53. As drive shaft 29 is rotated, a reciprocating motion istransmitted to rocker arm 53 by guide cam 59. The reciprocating motionof rocker arm 53 imp-arts the previously described axial motion tosliding member 51. Slot 57 allows vertical movement of cam follower 58during reciprocation of rocker arm 53. Guide cam 59 and rocker arm 53are again programmed so that sliding member 51 is positioned as shown inFIGURE 3 during the dwell period of the rotors and is withdrawn to allowupward movement of rotor 10 during rotation of the rotors.

This alternate locking and releasing of rotor 10 completely seals thecartridge chamber during firing and then allows the upper rotor to floatduring rotation such that no interference between the rotor surfaces ispresent.

Certain changes in design may occur to those skilled in the art Withoutdeparting from the invention. The preferred embodiment disclosed hereinutilizes but one of many possible mechanisms for alternately locking andfreeing the upper rotor. In some instances, it might be desirable to usea gas operated mechanism to drive cam member 51 rather than to use apurely mechanical linkage. In other applications, it might be desirableto provide means to drive the upper rotor directly from the drive shaft.herein constitutes a preferred embodiment, it will be understood thatthese and other changes may be made within the spirit of the invention.I therefore intend to be limited only by the scope of the appendedclaims.

I claim as my invention:

1. A machine gun, comprising:

aframe;

a gun barrel mounted in said frame having a bore;

a first cylindrical motor mounted in said frame for rotation about afirst longitudinal axis in parallel with said bore, said first rotorhaving a plurality of semi-cylindrical concave half chambers formedlongitudinally in the periphery thereof and positioned Although the formof the invention described therein so as to be successively aligned withsaid longitudinal axis in parallel with said first axis, said secondrotor having a plurality of semi-cylindrical concave half chamberscorresponding in size and number to the chambers in said first rotorformed longitudinally in the periphery thereof and positioned therein soas to be successively aligned with said bore during rotation of saidsecond rotor;

a Geneva wheel connected to said first rotor;

a crank operated continuously rotatable Geneva drive shaft mounted insaid frame and connected to said Geneva wheel, said Geneva wheelconverting. the continuous rotation of said drive shaft intointermittent rotation to thereby rotate said first rotor to successivelyalign said half chambers with said bore and to provide a timed dwellperiod for said first rotor after said alignment is achieved;

a sliding cam member extending through a slot in said frame and throughsaid axis ofsaid second motor to support said second rotor within saidframe;

- a rocker arm pivotally mounted on said frame having a first endconnected to said sliding cam member and a second cam follower endpositioned to follow a rotating guide cam mounted on said Geneva driveshaft;

said guide cam being designed to impart a reciprocating motion to saidrocker arm during rotation of said drive shaft, said sliding cam memberbeing moved axially by said rocker arm between a first position and asecond position, said sliding cam member in said first position having afirst portion thereon in said slot having dimensions corresponding tosaid slot to prevent lateral movement of said second rotor, said slidingcam member in said second position having a second portion thereon insaid slot with reduced dimensions with respect to said slot to allowlateral movement of said second rotor in a direction away from saidrotor;

and means for rotating said second rotor simultaneously with therotation of said first rotor, said guide cam being programmed to movesaid sliding cam member to said first position during the dwell periodof said first rotor and to move said sliding cam member to said secondposition during rotation of said first rotor.

2. A machine gun, comprising:

aframe;

a first cylindrical rotor mounted in said frame for rotation about afirst longitudinal axis; said first rotor having a plurality ofsemi-cylindrical concave half cartridge chambers formed longitudinallyin the periphery thereof;

a second cylindrical rotor mounted adjacent said first rotor in saidframe and being rotatable about a second longitudinalaxis in parallelwith said first axis, said second rotor having a plurality ofsemicylindrical concave half cartridge chambers corresponding in sizeand number to.the chambers in said first rotor formed longitudinally inthe periphery thereof;

a Geneva wheel connected to said first rotor;

driving means including a continuously rotatable Geneva drive shaftmounted in said frame and connected to said Geneva wheel, said Genevawheel converting the continuous rotation of said drive shaft intointermittent rotation to thereby rotate said first rotor to successivelyposition said half chambers in a cartridge firing position and toprovide a timed dwell period for said first rotor after said positioningis achieved;

a sliding cam member extending through a slot in said frame and throughsaid axis of said second rotor to support said second rotor within saidframe;

a rocker arm pivotally mounted on said frame having a first endconnected to said sliding cam member and a second cam follower endpositioned to follow a rotating guide cam mounted on said Geneva driveshaft;

7 said guide cam being designed to impart a reciprocating motion to saidrocker arm during rotation of said drive shaft, said sliding cam memberbeing moved axially by said rocker arm between a first position and asecond position, said sliding cam member in said first position having afirst portion thereon in said slot having dimensionscorresponding tosaid slot to prevent lateral movement of said second rotor, said slidingcam member in said second position having a second portion thereon insaid slot with reduced dimensions with respect to said slot to allowlateral movement of said second rotor in a direction away from saidfirst rotor; and

means for rotating said second rotor simultaneously with the rotation ofsaid first rotor, said guide cam being programmed to move said slidingcam member to said first position during the dwell period of said firstrotor and to move said sliding cam member to said second position duringrotation of said first- 3. A machine gun, comprising:

a frame;

a first rotor mounted in said frame for rotation about a first axis,said first rotor having a plurality of concave hal f cartridge chambersformed in the periphery thereof in parallel with said first axis;

a second rotor mounted adjacent said first rotor in said frame and beingrotatable about a second axis in parallel with said first axis, saidsecond rotor having a like plurality of concave half cartridge chambersformed in the periphery thereof;

a Geneva wheel connected to said first rotor;

continuously rotatable Geneva drive means mounted in said frame andconnected to said Geneva wheel, said Geneva wheel converting thecontinuous rotation of said drive means into intermittent rotation tothereby rotate said first rotor to successively position said halfchambers in a cartridge firing position and to provide a timed dwellperiod for said first rotor after said positioning is achieved;

a sliding cam member extending through a slot in said frame and throughsaid axis of said second rotor; means operated by said driving means foraxially reciprocating said sliding cam member between a first positionand a second position during rotation of said drive means, said slidingcam member in said first position having a first portion thereon in saidslot having dimensions corresponding to said slot to prevent lateralmovement of said second rotor, said sliding cam member in said secondposition having a second portion thereon in said slot with reduceddimensions with respect to said slot to allow lateral movement of saidsecond rotor in a direction away from said first rotor; and

means for rotating said second rotor simultaneously with the rotation ofsaid first rotor, said sliding cam member being programmed to move tosaid first position during the dwell .period of said first rotor and tomove to said second position during rotation of said first rotor.

4. A machine gun, comprising:

a frame;

first and second rotors mounted in said frame for individual rotationabout a pair of axes, each of said rotors having at least two concavehalf cartridge chambers formed in an outer surface thereof;

drive means for intermittently rotating said rotors to position a halfchamber in said first rotor adjacent a half chamber in said second rotorto form a complete single cartridge chamber, and to provide a timeddwell period after said chamber is formed;

a sliding cam member extending through a slot in said frame and throughsaid axis of said second rotor; means operated by said driving means foraxially reciprocating said sliding cam member between a first positionand a second position, said sliding cam member in said first positionhaving a first portion thereon in said slot having dimensionscorresponding to said slot to prevent lateral movement of said secondsecond rotor, said sliding cam member in said second position having asecond portion thereon insaid slot with reduced dimensions with respectto said slot to allow lateral movement of said second rotor in adirection away fro-m said first rotor; and

means for rotating said second rotor simultaneously with the rotation ofsaid first rotor, said sliding cam member being programmed to move tosaid first position during the dwell period of said first rotor and tomove to said second position during rotation of said first rotor.

References Cited by the Examiner UNITED STATES PATENTS 1,340,791 5/1920Paci fico 8913 2,317,579 4/1943 Bacon 89-33 X 2,965,004 12/1960 ShOelsonet al. 89-.126 2,977,854 4/1961 Wassel et al. 89-13 FOREIGN PATENTS123,246 11/1948 Sweden.

BENJAMIN A. BORCH-ELT, Primary Examiner.

S. W. ENGLE, Assistant Examiner.

1. A MACHINE GUN, COMPRISING: A FRAME; A GUN BARREL MOUNTED IN SAIDFRAME HAVING A BORE; A FIRST CYLINDRICAL ROTOR MOUNTED IN SAID FRAME FORROTATION ABOUT A FIRST LONGITUDINAL AXIS IN PARALLEL WITH SAID BORE,SAID FIRST ROTOR HAVING A PLURALITY OF SEMI-CYLINDRICAL CONCAVE HALFCHAMBERS FORMED LONGITUDINALLY IN THE PERIPHERY THEREOF AND POSITIONEDTHEREIN SO AS TO BE SUCCESSIVELY ALIGNED WITH SAID BORE DURING ROTATIONOF SAID FIRST ROTOR; A SECOND CYLINDRICAL ROTOR MOUNTED ADJACENT SAIDFIRST ROTOR IN SAID FRAME AND BEING ROTATABLE ABOUT A SECONDLONGITUDINAL AXIS IS PARALLEL WITH SAID FIRST AXIS, SAID SECOND ROTORHAVING A PLURALITY OF SEMI-CYLINDRICAL CONCAVE HALF CHAMBERSCORRESPONDING IN SIZE AND NUMBER TO THE CHAMBERS IN SAID FIRST ROTORFORMED LONGITUDINALLY IN THE PERIPHERY THEREOF AND POSITIONED THEREIN SOAS TO BE SUCCESSIVELY ALIGNED WITH SAID BORE DURING ROTATION OF SAIDSECOND ROTOR; A GENEVA WHEEL CONNECTED TO SAID FIRST ROTOR; A CRANKOPERATED CONTINUOUSLY ROTATABLE GENEVA DRIVE SHAFT MOUNTED IN SAID FRAMEAND CONNECTED TO SAID GENEVA WHEEL, SAID GENEVA WHEEL CONVERTING THECONTINUOUS ROTATION OF SAID DRIVE SHAFT INTO INTERMITTENT ROTATION TOTHEREBY ROTATE SAID FIRST ROTOR TO SUCCESSIVELY ALIGN SAID HALF CHAMBERSWITH SAID BORE AND TO PROVIDE A TIMED DWELL PERIOD FOR SAID FIRST ROTORAFTER SAID ALIGNMENT IS ACHEIVED; A SLIDING CAM MEMBER EXTENDING THROUGHA SLOT IN SAID FRAME AND THROUGH SAID AXIS OF SAID SECOND ROTOR TOSUPPORT SAID SECOND ROTOR WITHIN SAID FRAME; A ROCKER ARM PIVOTALLYMOUNTED ON SAID FRAME HAVING A FIRST END CONNECTED TO SAID SLIDING CAMMEMBER